The objectives of this work are to establish structure-function relationships in the allosteric enzyme glutamine synthetase from E. coli. 1) the structural work entails nmr, epr and fluorescence energy transfer experiments that will be used to establish distance relationships among the metal ions at the active site, the substrate and alosteric effector sites. 2) the functional relationships involve steady-state kinetics, rapid kinetic techniques (rapid quench and stopped-flow methods), isotope exchange from (180)Pi during net reaction. The use of pH variation of kinetic parameters and continued synthesis of various inhibitors that mimic transition-states will be made to gain insight into the enzymic mechanism. 3) further studies with the recently prepared Co(III)- and Cr(III)-enzymes will be made to determine the amino acids that serve as ligands to the metal ions. 4) further exploration of the theory of dipolar electronic relaxation will be undertaken for different metal ion pairs on glutamine synthetase. Our novel application of Mn2+ -Cr3+ electronic relaxation (EPR) to calculate distances will be expanded to include studies on allosteric interactions with glutamine synthetase. These studies are fundamental to the understanding of how allosteric effectors alter catalysis in regulatory enzymes. The three-dimensional relationships among the catalytic site, covalent adenylyl site and feedback inhibitor sites provide structural data about the control of glutamine biosynthesis at the enzyme level. Since the glutamine synthetase reaction is the pivotal reaction in nitrogen metabolism in cells, the research in this proposal is central to the understanding of the control of metabolism in normal cells. Understanding normal metabolism is basic to studies of abnormal disease states.